Hasil untuk "physics.space-ph"

Xiaoxin Zou, Xiaoxi Huang, A. Goswami et al.

Juan Liu, Yuran Huang, Anil Kumar et al.

Bradley A. Webb, Michael S. Chimenti, M. Jacobson et al.

D. Neri, C. Supuran

Niels Holten-Andersen, Matthew J. Harrington, H. Birkedal et al.

Ying-hong Guan, Jun Ma, Xu-chun Li et al.

J. Casey, S. Grinstein, J. Orlowski

Junyan Han, K. Burgess

Congcong Shen, J. Xiong, Huayong Zhang et al.

J. Rousk, P. Brookes, E. Bååth

G. Nicol, S. Leininger, C. Schleper et al.

G. W. Thomas

Soil pH is probably the single most informative measurement that can be made to determine soil characteristics. At a single glance, pH tells much more about a soil than merely indicating whether it is acidic or basic. For example, availability of essential nutrients and toxicity of other elements can be estimated because of their known relationship with pH. The term pH was "invented" by the Swedish scientist Sorensen (1909) in order to obtain more convenient numbers and the idea quickly caught on. Gillespie and Hurst (1918) seem to have been among the earliest to determine pH (or PH, as it was then called) electrometrically using a platinum-palladium blackhydrogen gas electrode, a calomel reference electrode and a fairly cumbersome potentiometer and galvanometer system. At that period, it was still much more common to use colorimetric methods with indicator dyes than the electrometric method. This changed rapidly, however. Sharp and Hoagland (1919) used a similar but less involved method than Gillespie and Hurst (1918) and Healy and Karraker (1922) used a commercially available platinum-hydrogen gas electrode, potentiometer and galvanometer which had been designed by Clark (1920). The decade of the 1920s saw the development of the quinhydrone electrode which was less fragile and much less expensive than the hydrogen-platinum electrode. But, it was the development of the glass electrode in the 1930s that brought the determination of pH very rapidly to its present importance and convenience. The Beckman Model G pH meter (circa 1931) was practically indestructible and could be used as a portable as well as a laboratory instrument. Although it was cumbersome by today's standards, it was virtually foolproof (except for the constantly failing batteries) and many are still capable of operating if not actually operating today. As recently as two decades ago, the use of the small, handheld portable pH meters then available to determine pH in the field was a very imprecise and hazardous undertaking because both electrodes and meters were subject to sudden failures but this has changed rather abruptly in the last few years. Microcircuitry and plastic have contributed to rugged pH meters and electrodes that withstand

K. Caldeira, M. Wickett, P. Duffy et al.

P. Gupta, K. Vermani, S. Garg

G. Helmlinger, F. Yuan, M. Dellian et al.

N. Tanner, Yinhua Zhang, T. C. Evans

Nucleic acid amplification is the basis for many molecular diagnostic assays. In these cases, the amplification product must be detected and analyzed, typically requiring extended workflow time, sophisticated equipment, or both. Here we present a novel method of amplification detection that harnesses the pH change resulting from amplification reactions performed with minimal buffering capacity. In loop-mediated isothermal amplification (LAMP) reactions, we achieved rapid (<30 min) and sensitive (<10 copies) visual detection using pH-sensitive dyes. Additionally, the detection can be performed in real time, enabling high-throughput or quantitative applications. We also demonstrate this visual detection for another isothermal amplification method (strand-displacement amplification), PCR, and reverse transcription LAMP (RT-LAMP) detection of RNA. The colorimetric detection of amplification presented here represents a generally applicable approach for visual detection of nucleic acid amplification, enabling molecular diagnostic tests to be analyzed immediately without the need for specialized and expensive instrumentation.

Volkan Yesilyurt, M. Webber, Eric A. Appel et al.

M. Koziolek, M. Grimm, D. Becker et al.

Igor Bargatin, Dengge Jin, Zaini Alansari et al.

We propose a tether-based structural architecture for orbital data centers operating in Dawn-Dusk Sun-Synchronous (DDSS) orbits under continuous sunlight. These space-based data centers, powered solely by solar energy, could provide multi-megawatt computing for artificial intelligence (AI) inference with minimal latency to Earth. The proposed design uses a tethered chain of computing nodes with photovoltaic panels to achieve uninterrupted 2-20 MW of computing power, and employs radiative cooling and integrated shielding to manage heat and radiation. We detail the system architecture, including mass budgets, passive attitude control, and the dynamics induced by micrometeoroid collisions.

Ilja Honkonen, Riku Jarvinen, David Phillips

We present a new algorithm for numerical magnetohydrodynamics on staggered meshes preserving $\nabla \cdot B = 0$. Our algorithm is based on the constrained transport method and supports both cell-based adaptive mesh refinement and temporal substepping. We handle resolution changes directly on the logically Cartesian grid without needing interpolation or projection between nested or neighboring grids, nor coupling the solution between refinement levels.